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Vibrating Wire Piezometers <br />Five vibrating wire piezometers, designated VWP -01 through VWP -05, were installed in <br />coal refuse at CWDA No. 2 in June 2005. The piezometers were grouted in drilled <br />boreholes as described by BGI (2006). Piezometer locations are presented on the <br />attached site plan. Since installation two of the vibrating wire piezometers have stopped <br />working correctly (VWP -01 and VWP -04). Diagnostic tests indicate that shorts have <br />developed, likely due to damaged cables. Three additional vibrating wire piezometers, <br />designated VWP -06 through VWP -08, were installed at CWDA No. 2 in June 2009 to <br />supplement the remaining piezometers. Completion details of these piezometers are <br />described by BGI (2009). Due to damage to existing vibrating wire piezometers, an <br />additional two VWP's (VWP -9 and VWP -10) were installed on May 18, 2012. During the <br />September 2, 2013 site visit we were able to extract information at installations VWP -05, <br />06, 08, 09 and 10, which provides good lateral representation of the coal waste in CDWA <br />No. 2. <br />Pore pressures measured to date are presented on the attached Pore Plat figure. Pore <br />pressures at VWP -06, VWP -08. VWP -09 and VWP -10 were constant during the 3rd <br />quarter of 2013. Those reading are consistent with little or no new gob material at those <br />sites and the readings indicate generally stable conditions at those piezometer sites. <br />Readings at these piezometers have generally decreased since they were installed. This is <br />a good indication that internal drainage is occurring and that waste material is <br />dewatering due to consolidation and trending towards equilibrium. All measured pore <br />pressures are well below the pore pressures at failure for similar confining pressures for <br />the CU triaxial shear tests that have been conducted as part of the on -going stability <br />evaluation for this refuse bank. Readings at VWP -05 increased slightly indicating the <br />effects of new gob being placed on the pile and pore pressures reacting to this new <br />material. <br />Pore pressures are anticipated to continue to decrease as drainage occurs. In any event, <br />on -going monitoring of all piezometers is recommended to monitor pore pressure <br />responses to the on -going refuse placement. Otherwise, the measured pore pressures <br />are consistent with the revised stability evaluation for the coal refuse performed by BGI <br />(2008). <br />Site Visit io s <br />During my site visit on September 17, 2013 with you and Ms. Tamme Bishop of J.E. <br />Stover & Associates, I noted the following items of interest to monitor as compaction and <br />grading operations at CWDA No. 2 continue: <br />1. Several small wet areas were noted in depressions near the top of the gob pile. <br />These were in areas of uncompacted gob that was to be spread and compacted <br />and were the result of recent rain storms not dewatering. Water was observed to <br />be flowing in the dewatering ditches adjacent to the Gob Pile #2 haul roads and <br />appeared to be function well as Photo 1 attached indicates. <br />3rd Qtr Monitoring Report.doc PN #05- 126 -GEO <br />Page 2 of 5 <br />